A. Field of the Invention
The invention relates to cell transplantation in an animal body, and comprises a carrier for cells to be implanted.
B. Prior Art
Attempts have been made to create mechanical immune barriers for transplantation of endocrine cells. In these devices, microporous membranes separate the transplanted cells from the host's immune rejecting cells and proteins (immunoglobulins) but allow desired nutrients and oxygen to sustain these cells and the desired hormonal products produced by the cells to benefit the host. The main application of these hybrid devices is in the treatment of diabetes mellitus in which an insulin deficiency in the host is treated by transplanting insulin producing beta cells from the islets of Langerhans of the pancreas contained within the devices.
In general, there have been three principal types of microporous hybrid endocrine devices, namely, devices that are incorporated in a vascular shunt; macroencapsulated devices in which clusters of endocrine (islet) cells are enclosed in a microporous membrane; and microencapsulated devices in which a single or small number of endocrine cells (islets) are enclosed in a spherical microporous membrane. In all three types of devices, allographs or xenographs have been used.
These devices have shown promising results in reducing or eliminating the need for exogenous insulin therapy in diabetic animals; however, because of poor diffusional characteristics, none of these devices have been shown to respond rapidly enough to post prandial or fluctuating blood glucose levels to affect the tight glucose control necessary to prevent the long term complications of diabetes, such as nephropathy, neuropathy, premature atherosclerosis, and retinopathy and blindness.
In this invention, a novel micro and macro encapsulation geometry is described which overcomes these deficiencies.